Electromagnetic Pulse Waveform Research Articles

Improving the Detection Effect of Long-Baseline Lightning Location Networks Using PCA and Waveform Cross-Correlation Methods

Ultra-long-distance and high-precision lightning location technology is an important means to realize low-cost and wide-area lightning detection. This paper carried out research on the high-precision location technology of very-low-frequency (VLF) lightning electromagnetic pulse based on the Asia-Pacific Lightning Location Network (APLLN) deployed in 2018. Two key technologies are proposed in this paper: one is the calculation method of signal arrival time using very-low-frequency lightning electromagnetic pulse waveform, and the other is the compression transmission technology of lightning electromagnetic pulse waveform based on a signal principal component analysis. The results of a comparison and evaluation of the improved APLLN with the ADTD system show that the APLLN has a relative location efficiency of 69.1% and an average location error within the network of 4.5 km.

A Highly Sensitive and Miniature Optical Fiber Sensor for Electromagnetic Pulse Fields.

The detection of an electromagnetic pulse (EMP) field is of great significance in determining the field environment of tested equipment in small spaces. Finger-shaped miniature optical fiber sensors for electromagnetic pulse field measurement were designed. The antenna of a weak field sensor was integrated with a shielding shell, and the wire welded at the direct electro-optic converting circuit connected to an optical fiber through special structure and circuit design was taken as the antenna of a strong field sensor. Measurements in the time domain and frequency domain had been carried out for the two sensors. Experiment results demonstrate that the weak field sensor and the strong field sensor have flat responses from 100 kHz to 1 GHz with a variation of 2.3 dB and 2.9 dB, respectively, and the EMP waveform detected by the sensors agrees well with the applied standard square wave. Moreover, the strong field sensor exhibits linear responses from 645 V/m to 83 kV/m. The resolution of the weak field sensor is as low as 13 V/m. The result indicated that the designed sensors had good performance.

Electromagnetic radiations from laser interaction with gas-filled Hohlraum

The emission of intensive electromagnetic pulse (EMP) due to laser-target interactions at the ShenGuang-III laser facility has been evaluated by probes. EMP signals measured using the small discone antennas demonstrated two variation trends including a bilateral oscillation wave and a unilateral oscillation wave. The new trend of unilateral oscillation could be attributed to the hohlraum structure and low-Z gas in the hohlraum. The EMP waveform showed multiple peaks when the gas-filled hohlraum was shot by the high-power laser. Comparing the EMP signals with the verification of stimulated Raman scattering energy and hard x-ray energy spectrum, we found that the intensity of EMP signals decreased with the increase of the hohlraum size. The current results are expected to offer preliminary information to study physical processes on laser injecting gas-filled hohlraums in the National Ignition Facility implementation.

Development of One-Dimensional Norm Detector for Nanosecond-Level Transient Electric Field Measurement

This paper develops a one-dimensional norm detector for nanosecond-level transient electric field (E-field) measurement based on the digital measurement technology. It has two main advantages over the traditional measurement method. First, the measured signals can be stored and no transmission line is needed. Hence, it can detect the E-field coupled in hermetically sealed cavities, such as the cockpit of an aircraft or a vehicle under electromagnetic compatibility test. Second, commonly used norms of the measured waveform can be acquired by the signal processing software quickly and conveniently. Therefore, the efficiency of the measurement experiment can be improved. This paper describes the detailed realization of the norm detector and the design of its signal processing software. The maximum sampling rate of the norms detector is 2 GSPS and the memory depth is 8 kB. Via adjusting the height of the antenna, the measuring range can be 0.1–55 kV/m and the estimated operation bandwidth is 1 kHz–460 MHz. The norm detector is tested and compared with the traditional E-field sensor with the fiber-optic link by measuring the square waveform and the actual electromagnetic pulse waveform. Furthermore, the norm detector can measure magnetic field, coupled current or high-voltage pulse by a simple structural modification.

Numerical Simulation of the HEMP Environment

This paper develops the program MCHII, numerically simulating the physical process of Compton electron currents scattered by the interaction of γ rays with ambient air molecules radiating the early time electromagnetic pulse (E1) during the high altitude nuclear explosion. The paper discusses the waveform characteristics of the electromagnetic pulse E1 as it propagates toward the ground from beneath the explosion point during the high altitude nuclear explosion, and provides a detailed study with regard to the influence of explosion height, energy, and γ spectrum. Numerical simulations are used to present the waveform characteristics of the electromagnetic pulse after going through the ionized layer above the explosion point after the high altitude nuclear explosion, and the paper presents the distribution of high altitude electromagnetic pulse waveform amplitudes at satellite orbits.

Time-domain simulation and waveform reconstruction for shielding effectiveness of materials against electromagnetic pulse

Shielding effectiveness (SE) of materials of current testing standards is often carried out by using continuous-wave measurement and amplitude-frequency characteristics curve is used to characterize the results. However, with in-depth study of high-power electromagnetic pulse (EMP) interference, it was discovered that only by frequency-domain SE of materials cannot be completely characterized by shielding performance of time-domain pulsed-field. And there is no uniform testing methods and standards of SE of materials against EMP. In this paper, the method of minimum phase transfer function is used to reconstruct shielded time-domain waveform based on the analysis of the waveform reconstruction method. Pulse of plane waves through an infinite planar material is simulated by using CST simulation software. The reconstructed waveform and simulation waveform is compared. The results show that the waveform reconstruction method based on the minimum phase can be well estimated EMP waveform through the infinite planar materials.

Electro-Thermo-Mechanical Characterizations of Various Wire Bonding Interconnects Illuminated by an Electromagnetic Pulse

A comprehensive electro-thermo-mechanical transient investigation is carried out to characterize time-dependent thermal and mechanical responses of metal wire bonding interconnects, as they suffer from the impact of an electromagnetic pulse (EMP) with different current or voltage waveforms. In our mathematical implementation, a hybrid time-domain finite element method is applied to simulate mutual interactions among electrical, thermal, and mechanical fields, with all nonlinearities of temperature-dependent electrical conductivities, thermal conductivities, thermal expansion coefficients, and even the Young's modulus of materials being treated appropriately. The developed algorithm is partially validated by computing transient temperature and thermal stress of other interconnects with good agreement with reference results. Parametric studies are performed to show the effects of EMP waveform parameters, geometrical and physical parameters of various wire bonding interconnects on their transient thermal and mechanical responses, thus providing basic information for their electromagnetic protection so as to suppress the impact of an intentional EMP.

TRANSIENT RESPONSES OF SOME ANTENNAS UNDER THE IMPACT OF AN INTENTIONALLY INCIDENT HIGH-POWER ELECTROMAGNETIC PULSE

An improved flnite difierence time domain (FDTD) method is employed for fast capturing transient responses of reconflgurable and multiple-input-multiple-output (MIMO) antennas under the impact of an intentional high-power electromagnetic pulse (EMP) but with difierent waveforms, respectively, where lumped element and sub-cellular thin-wire algorithms and coaxial feed model are integrated together for handling such three-dimensional antennas used for wireless communication. Parametric studies are carried out to show efiects of high-power EMP waveforms, its polarization state and incident direction on the transient coupled voltages on the coaxial feed line and across the diodes, with su-cient information obtained for understanding the interaction between the EMP and the antennas.

Numerical simulation of the early-time high altitude electromagnetic pulse

In this paper, the finite difference method is used to develop the Fortran software MCHII. The physical process in which the electromagnetic signal is generated by the interaction of nuclear-explosion-induced Compton currents with the geomagnetic field is numerically simulated. The electromagnetic pulse waveforms below the burst point are investigated. The effects of the height of burst, yield and the time-dependence of γ-rays are calculated by using the MCHII code. The results agree well with those obtained by using the code CHAP.

Time-of-arrival prediction model for transionospheric EMP

An ionospheric-delay correction model that measures the time of arrival (TOA) of transionospheric electromagnetic pulse (EMP) is presented. The pulse-broadening effect due to ionosphere is incorporated into the ionospheric group delay model to provide more accurate delay correction for measuring EMP TOA. The predictions of the model are compared with laboratory test results for various total electron content. This model also enables us to evaluate the sensitivity of TOA performance to changes in the receiver hardware parameters, e.g. filter bandwidth and the threshold levels in the time-tagging process of the EMP waveform.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

A bound on aperture coupling from realistic EMP

Rigorous modification of the step function electromagnetic pulse (EMP) energy bound, for apertures, to the more realistic description of an EMP waveform is carried out. The double exponential EMP waveform is used first and a general formula is derived for the energy scattered and absorbed by the aperture. This result shows that for very small apertures the energy can be quite small compared to the previous step function result. However, it is indicated that, in principle, if no further conditions are imposed on the structures behind the aperture (or attached to the aperture), the smallest applicable bound is the previous step function bound. Finally, the inverse exponential EMP waveform (with more realistic high-frequency spectrum) is used with very small apertures to obtain even smaller energy bounds than the double exponential waveform result. >

Development of a New High Altitude Electromagnetic Pulse (Hemp) Environment and Resulting Overhead Line Responses

Being able to accurately determine the response of an electrical system which is excited by a high altitude nuclear electromagnetic pulse (EMP) requires a knowledge of the time history of the incident EMP field strength, as well as its angle of incidence and polarization. A commonly used, unclassified, description of this environment is provided by the ''Bell Laboratory waveform.'' Recent studies have shown, however, that this EMP waveform tends to overestimate the response of an above-ground transmission line by more than an order of magnitude. As a result, other unclassified high altitude EMP environments have been developed. This presentation discusses the development of two alternate unclassified EMP environment descriptions: one arising from a simple radiating dipole moment model, and the other resulting from curve-fitting the calculated fields from a computer code named CHAP. For both of these EMP models, the electric field at two earth observation points are compared. These fields are then coupled to an above-ground line and the resulting open-circuit voltage responses are compared. Using the CHAP EMP environment, a limited parametric study of the peak positive and negative open-circuit voltage is then performed and surface plots of these peak voltages are presented. 8 refs., 21 figs., 1more » tab.« less

Numerical Analysis of a Transmission Line EMP Simulator

A theoretical model is defined for an electromagnetic pulse (EMP) simulator for testing EMP effects on high altitude satellites. The simulator is composed of three flat-plate transmission line sections. The first and third sections are tapered to accommodate, respectively, a generator and a terminating resistor. This problem is analyzed in the frequency domain over those frequency components which are known to contribute most significantly to a typical EMP waveform. The analysis uses a numerical technique to solve the basic problem of an unknown current distribution on a curved, tapered strip, excited by a known electric field. The unknown current is solved by the method of moments, using triangular basis functions. As a check, input impedances are computed for the triangular dipole, showing good agreement with experimental results. For the transmission line simulator, computed input impedance, VSWR, power dissipated in the terminating resistor, and the power lost to radiation are presented as a function of frequency. The computed current distributions are used to calculate the electric fields between and immediately beyond the parallel plates. Although a considerable portion of power is converted to radiation at the higher frequencies, it is shown that at least within the working volume the electric field maintains a reasonably constant level.